The present invention relates to a method of processing a rotor and to, a motors and a hard disk drive unit.
A motor used for a hard disk drive unit has a construction in which a rotor is cap-shaped as a whole and a magnet is assembled at the inside of the cap-shaped rotor through a ring-shaped yoke, or is attached to the rotor directly because a shaft portion where hard disks are attached is integrally formed with the rotor of the motor.
In the constitution in which the shaft portion for attaching a driven body to the rotor is formed like integrally that described above, it is neccessary for a center line of the ring-shaped magnet attached at the inside of the cap-shaped rotor, a center line of the shaft portion, and a center line of an attaching hole for attaching the shaft to support the rotor to rotatively match.
However, in the prior method of processing this kind of rotor, it has been difficult to match center lines of these parts because the main body of the rotor and the magnet are produced in separated proceed and the magnet is attached after attaching the yoke to the completed main body of the rotor.
Thus, a magnetic gap formed between the magnet of the rotor and the core of coil of a stator does not become uniform when the rotor is assembled with the stator, rotation of the rotor and rotation of the driven body formed at a shaft portion of the rotor lack smoothness, and an inconvenience exist in that vibration is generated and the sound of rotation becomes large or is likely to occur.
Therefore, when a hard disk driving unit is constructed using this kind of motor, the motor had a problem in that such an inconvenience occurs during an operation of reading out and writing data.
An object of the present invention is to provide a method of processing a rotor of a motor, a motor, and a hard disk driving unit using the motor to provide smooth rotation of the driven body formed at the rotor and the shaft portion of the rotor.
According to a first aspect of the invention, a method of processing a rotor comprises a step of forming a shaft portion outside of a main body of the cap-shaped rotor as a whole and a step attaching a ring-shaped magnet at the inside of the main body of the rotor. Further, a method of working an attaching hole of the shaft fixed at the shaft portion and the main body of the rotor standardizing the inner circumferential face of the magnet is provided.
By performing the required working for standardizing the inner circumferential face of the magnet after attaching the magnet at the main body of the rotor, the center line of the magnet, rotation axis of the main body of a rotor, and the center line of the shaft portion can be matched easily and accurately. As a result, in the case that the motor is assembled with a stator, magnetic gap formed between the rotor and the stator can be uniform and smooth rotation of the driven body formed at the rotor and the shaft portion of the rotor can be maintained so as to decrease the sound of rotation.
According to the present invention, a hard disk drive unit in which a motor using the rotor manufactured like that above-described is constituted and magnetic disks are fixed at the main body of the rotor.